Using radar systems in motor vehicles, it is possible to measure the distance to other vehicles and also, using the Doppler effect, the relative speeds of other vehicles or other objects in the surroundings of the vehicle. Conventionally, they have been used to automatically bring the speed of the host vehicle in line with the speed of a preceding vehicle and to regulate the distance to the preceding vehicle.
Furthermore, in the case of radar systems which in particular also make it feasible to monitor the traffic in adjacent lanes, there are many motor vehicle applications, e.g., parking or reverse assist systems for blind-spot object detection, pre-crash functions, stop & go functions and the like. Pre-crash functions are functions which allow an upcoming collision to be automatically detected and averted or at least mitigated via intervention in the brake system, drive system and/or steering system and/or allow timely configuration of passive safety systems, e.g., seatbelt tighteners or airbags, with regard to the upcoming collision. Stop & go functions constitute a further refinement of conventional distance control systems, and in congested or city traffic allow the vehicle to be automatically braked to a standstill and if necessary move off again if the preceding vehicle moves off. As these functions are mainly used in the lower speed range and in rapidly changing traffic situations, it is particularly important to monitor the traffic in adjacent lanes.
A further possible application for radar systems of the aforementioned kind is a lane-change assistant, which helps the driver change lanes on multi-lane roads, e.g., to prevent collisions with passing vehicles.
For all the aforementioned functions, in particular radar systems having a short or medium range are used to monitor the immediate surroundings of the host vehicle, and which also provide as much spatial resolution as possible. Pulsed radar systems are particularly suitable for this purpose.
In the case of long-range radar systems such as those used for distance regulation, angular resolution systems, e.g., multiple beam radar systems are used which use a plurality of antenna patches to generate a plurality of overlapping radar lobes having slightly different emission directions and allow angular information regarding the located objects to be obtained via analysis of the phase position of the radar echo, so that as part of distance regulation a distinction can be made between vehicles in the same lane as the host vehicle and traffic in adjacent lanes.
By contrast, in the case of systems having a shorter range, which in particular also allow the area surrounding the rear of the vehicle to be monitored, conventional designs use a plurality of separate radar sensors, each of which is designed and specifically positioned for a specific monitoring task. For example, in the case of one of these designs a total of four radar sensors are provided, which are situated in pairs on both sides of the vehicle. One sensor of each pair generates a radar lobe oriented obliquely backwards for detecting vehicles in the adjacent lane and behind the host vehicle, and the second sensor of the pair generates a radar lobe oriented sideways, preferably roughly at the height of the rear bumper of the host vehicle, for illuminating the blind spot in the immediate vicinity of the host vehicle.